This invention relates to pressure relief valves and more particularly to a manually adjustable multi-position relief valve.
It is common practice to employ a pressure gauge, a pressure relief valve, or both in association with compressors, or other sources of fluid under pressure, to indicate over-pressure conditions and/or to allow for escape of pressurized fluid in case of an over-pressure condition. Pressure relief valves are generally designed to provide relief at a given pressure value. Some pressure relief valves provide adjustment, such as by turning an adjustment screw which is linked through a suitable mechanism to the valve closure mechanism which maintains the relief valve closed in the absence of pressure exceeding the preset limit. However, such arrangements provide only a small adjustment in the valve pressure limit, and adjustment of the pressure limit generally requires the use of a pressure gauge as a reference while the adjustment is being made to insure that the desired limit value is obtained.
It is apparent that different applications require different limit settings for pressure relief valves. For example, a relatively low limit in the order of 35 psi may be desirable for compressed air in a spray painting operation, whereas a higher limit, in the order of 50 to 75 psi, may be desired when filling a bicycle tire with air. Other applications may require higher or lower pressure limit settings. Thus, it would be desirable to have a pressure relief valve capable of adjustment over a wide range of pressure limits and which in use indicates the limit value without the requirement of a pressure gauge. Further, it would be desirable to have such pressure relief valve of this type which is easy to use and economical to manufacture.